Cocaine dependence and violence are serious public health problems that are often related. There are many biological features of these behaviors that are poorly understood. Further research will elucidate mechanisms and contribute to the development of more effective treatments for impulsive behaviors including cocaine use and the associated violence. Low serotonin (5-HT) function is associated with increased aggressive and impulsive behavior in individuals with antisocial personality disorder (ASP). These same individuals have a high probability of substance dependence. Thus, the association between substance abuse and impulsive and aggressive behavior is complex and may be influenced both by the pharmacologic effects of drugs themselves and the fact that individuals who abuse drugs are also more prone to these behaviors. Although some studies find that cocaine increases aggressive behavior in laboratory animals, most animal studies do not find an increase in aggression after cocaine administration. Epidemiological studies find an association between cocaine and violence, but few laboratory studies have examined this issue in humans. In preliminary studies by our group, we have not found that acute doses of cocaine or recent chronic cocaine use increase aggressive responding in humans. The specific aims of this proposal are: Aim 1: To determine the effects of recent chronic cocaine use and cocaine abstinence/withdrawal on impulsive and aggressive responding in female and male cocaine dependent subjects with ASP with a history of childhood violent behavior, and in matched cocaine dependent subjects without ASP and to compare this responding to matched healthy controls. Aim 2: To measure 5-HT function using a neuroendocrine challenge and relate this measure to impulsive and aggressive responding in cocaine dependent subjects with ASP with a history of childhood violent behavior, in matched cocaine dependent subjects without ASP who have been off cocaine for at least two weeks and in healthy controls. Aim 3: To determine if chronic administration of the 5-HT agonist buspirone decreases impulsive and aggressive responding and cocaine use in subjects with ASP with a history of childhood violent behavior. Preliminary results from research performed thus far finds that: - Cocaine dependent subjects with a history of aggression in childhood are more aggressive on laboratory measures of aggression than those without this history. - Aggressive responding decreases as subjects withdraw from cocaine. - The amount of aggressive responding correlates with the severity of cocaine withdrawal symptoms.